Risk · tool 6 of 7
Monte Carlo Simulation
Monte Carlo Simulation: replaces one date with a range and a probability.
Best for: Large schedules and budgets · Time: Half a day with a tool
Domain: Risk · Focus area: Monitoring and Controlling
How it works
A simulation runs the plan thousands of times, varying durations and costs within estimated ranges. The output tells you the chance of finishing by each date.
- Quality depends on the input ranges.
- Include correlated risks.
- Report confidence levels, such as P80.
How to apply it
- Give key tasks a three-point range.
- Add major risks.
- Run the simulation in your tool.
- Report the dates at P50 and P80.
In practice
The plan says June. The simulation gives 15% by June and 80% by mid-August.
Pro tip
“80% confident by August” is a stronger promise than “June, hopefully”.
Use it
- Playbook: We are going to miss the date
- Case study: Crossrail (Elizabeth line)
Quick check
What does P80 mean?
Sources
- PMBOK® Guide, 8th edition, and The Standard for Project Management (PMI, 2025)
Last reviewed 2026-11-02 against the PMBOK® Guide, 8th edition · Practitioner review pending · How this guide is made